Particle accelerator and particle beam therapy apparatus

Abstract

Disclosed a particle accelerator that accelerates a charged particle beam while circulating the charged particle beam as a circulating beam and outputs some of the circulating beam as an output beam, the particle accelerator including: a first deflection section and a second deflection sections each having a deflection electromagnet; a first straight section, a second straight section, and third straight section each not having the deflection electromagnet; and a control unit, wherein a preceding output deflector of the first straight section deflects some of the circulating beam toward an inner side of a circulating trajectory of the circulating beam to separate the some of the circulating beam as an output beam, wherein a succeeding output deflector of the third straight section deflects the output beam separated from the circulating beam by the preceding output deflector toward an outer side of the circulating trajectory of the circulating beam, and wherein the control unit controls at least the quadrupole electromagnet such that a phase advance of a betatron oscillation of the output beam is 270±45 degrees in a section from the preceding output deflector to the succeeding output deflector.

The invention claimed is: 
     
       1. A particle accelerator that accelerates a charged particle beam while circulating the charged particle beam as a circulating beam and outputs some of the circulating beam as an output beam, the particle accelerator comprising:
 a plurality of deflection sections each having a deflection electromagnet; 
 a plurality of straight sections each not having the deflection electromagnet; and 
 a control unit, 
 wherein the plurality of straight sections include 
 a first straight section having a preceding output deflector, 
 a second straight section that is disposed on a downstream side of the first straight section in a traveling direction of the circulating beam and has a quadrupole electromagnet, and 
 a third straight section that is disposed on a downstream side of the second straight section in the traveling direction of the circulating beam and has a succeeding output deflector, 
 wherein the plurality of deflection sections include 
 a first deflection section connecting the first straight section and the second straight section to each other, and 
 a second deflection section connecting the second straight section and the third straight section to each other, 
 wherein the preceding output deflector deflects some of the circulating beam toward one of an inner side and an outer side of a circulating trajectory of the circulating beam to separate the some of the circulating beam as an output beam, 
 wherein the succeeding output deflector deflects the output beam separated from the circulating beam by the preceding output deflector toward the other of the inner side and the outer side of the circulating trajectory of the circulating beam, and 
 wherein the control unit controls at least the quadrupole electromagnet such that a phase advance of a betatron oscillation of the output beam is 270±45 degrees in a section from the preceding output deflector to the succeeding output deflector. 
 
     
     
       2. The particle accelerator according to  claim 1 ,
 wherein the control unit controls at least the quadrupole electromagnet such that a phase advance of a betatron oscillation of the output beam is 270±45 degrees in a section from the preceding output deflector to the succeeding output deflector, and 
 wherein the control unit controls the preceding output deflector such that the output beam passes through the vicinity of a passage region of the circulating beam in the first deflection section, the output beam passes through a passage region of the circulating beam in the second deflection section or passes through the vicinity of the passage region of the circulating beam in the second deflection section, and the output beam passes through a position spaced apart from a passage region of the circulating beam in third straight section. 
 
     
     
       3. The particle accelerator according to  claim 1 , wherein the first straight section and the third straight section are disposed at positions facing each other on the circulating trajectory of the circulating beam. 
     
     
       4. The particle accelerator according to  claim 3 , wherein the first straight section and the third straight section extend parallel to each other. 
     
     
       5. The particle accelerator according to  claim 1 ,
 wherein each of the plurality of deflection sections has the deflection electromagnet and a deflection section quadrupole electromagnet or has a quadrupole magnetic field generating mechanism for a deflection section obtained by integrating the deflection electromagnet and a quadrupole magnetic field coil, 
 wherein each of the plurality of straight sections has the quadrupole electromagnet, and 
 wherein the control unit adjusts an amount of excitation of the deflection section quadrupole electromagnet of each of the plurality of deflection sections or an amount of excitation of the quadrupole magnetic field generating mechanism for a deflection section and an amount of excitation of the quadrupole electromagnet of each of the plurality of straight sections such that a phase advance of a betatron oscillation of the output beam is 270±45 degrees in a section from the preceding output deflector to the succeeding output deflector. 
 
     
     
       6. The particle accelerator according to  claim 5 ,
 wherein the control unit adjusts an amount of excitation of the deflection section quadrupole electromagnet of each of the plurality of deflection sections or an amount of excitation of the quadrupole magnetic field generating mechanism for a deflection section and an amount of excitation of the quadrupole electromagnet of each of the plurality of straight sections such that a phase advance of a betatron oscillation of the output beam is 270±45 degrees in a section from the preceding output deflector to the succeeding output deflector, and 
 wherein the control unit adjusts electric field intensity of the preceding output deflector such that the output beam passes through the vicinity of a passage region of the circulating beam in the first deflection section, the output beam passes through a passage region of the circulating beam in the second deflection section or passes through the vicinity of the passage region of the circulating beam in the second deflection section, and the output beam passes through a position spaced apart from a passage region of the circulating beam in third straight section. 
 
     
     
       7. The particle accelerator according to  claim 1 ,
 wherein each of the plurality of straight sections has the quadrupole electromagnet, and 
 wherein the control unit adjusts the quadrupole electromagnet of each of the plurality of straight sections such that a phase advance of a betatron oscillation of the output beam is 270±45 degrees in a section from the preceding output deflector to the succeeding output deflector. 
 
     
     
       8. The particle accelerator according to  claim 7 ,
 wherein the control unit adjusts the quadrupole electromagnet of each of the plurality of straight sections such that a phase advance of a betatron oscillation of the output beam is 270±45 degrees in a section from the preceding output deflector to the succeeding output deflector, and 
 wherein the control unit adjusts electric field intensity of the preceding output deflector such that the output beam passes through the vicinity of a passage region of the circulating beam in the first deflection section, the output beam passes through a passage region of the circulating beam in the second deflection section or passes through the vicinity of the passage region of the circulating beam in the second deflection section, and the output beam passes through a position spaced apart from a passage region of the circulating beam in third straight section. 
 
     
     
       9. The particle accelerator according to  claim 1 , wherein a deflection angle of the charged particle beam caused by the first deflection section is 60 degrees or more. 
     
     
       10. The particle accelerator according to  claim 1 , wherein a total deflection angle of the charged particle beam caused by the first deflection section and the second deflection section is 180 degrees. 
     
     
       11. The particle accelerator according to  claim 1 ,
 wherein each of the first straight section and the third straight section has the quadrupole electromagnet, 
 wherein the preceding output deflector is disposed on a downstream side of the quadrupole electromagnet of the first straight section in the traveling direction of the circulating beam, and 
 wherein the succeeding output deflector is disposed on a downstream side of the quadrupole electromagnet of the third straight section in the traveling direction of the circulating beam. 
 
     
     
       12. The particle accelerator according to  claim 1 ,
 wherein the quadrupole electromagnet of the first straight section is disposed substantially at a center of the first straight section in the traveling direction of the circulating beam, and 
 wherein the quadrupole electromagnet of the third straight section is disposed substantially at a center of the third straight section in the traveling direction of the circulating beam. 
 
     
     
       13. A particle beam therapy apparatus comprising:
 the particle accelerator according to  claim 1 ; and 
 an irradiation device that transports the charged particle beam extracted as the output beam from the particle accelerator and irradiates an irradiation target.